Except where specifically noted, the life-history information presented
below applies to
coastal steelhead and does not include inland steelhead of the Columbia and
Fraser River
Basins.

Anadromy-Nonanadromy

The question of the relationship between anadromous and nonanadromous forms
of
salmonid species has been widely examined, perhaps most intensively for sockeye
and kokanee
salmon (O. nerka). Foote and Larkin (1988) examined assortative mating
between sockeye
and kokanee salmon and found that male mate choice was dominated by form; that
is, kokanee
males demonstrated preference to spawn with kokanee females rather than sockeye
females.
Neave (1944) determined that anadromous and nonanadromous O. mykiss of the
Cowichan
River, Vancouver Island, constituted distinct "races" based on scale counts and
migration
behavior.

Allendorf (1975) found that the genetic distinction between coastal and
inland
O. mykiss applies to both life-history forms; that is, rainbow trout east
of the Cascades are
genetically more similar to steelhead from east of the Cascades than they are to
rainbow trout
west of the Cascades. Most recent studies of O. mykiss have focussed on
either rainbow trout
or steelhead and thus provide no direct information about the relationship
between the forms
on a finer geographic scale. However, some protein electrophoretic studies that
have reported
data only for "rainbow trout" probably included samples of steelhead as well (Currens - footnote 2 ). For
example, in the John Day River, an Oregon tributary of the Columbia River,
genetic
differences between O. mykiss from the North and South Forks were larger
than differences
between presumed steelhead and rainbow trout in the South Fork (Currens et al.
1987). In the
Deschutes River, another Oregon tributary of the Columbia River, Currens et al.
(1990) found
much larger genetic differences between O. mykiss from above and below a
barrier falls than
between presumed steelhead and rainbow trout from below the falls.

In a study of mitochondrial DNA (mtDNA) in O. mykiss, Wilson et al.
(1985) found
that coastal populations of steelhead and rainbow trout were distinct from each
other, even
when sampled from the same river basin. However, steelhead and rainbow trout
from interior
British Columbia clustered in the same clonal line as rainbow trout from Alberta.
Interpretation of these results is difficult because of the small sample sizes
and dispersed
sampling that included rainbow trout from California and Alberta whereas all
steelhead
samples were from British Columbia. Furthermore, Buroker (footnote 3) found that a mtDNA marker
Wilson et al. (1985) reported as characteristic of rainbow trout was the most
common marker
in Buroker's study of North American steelhead.

Steelhead Run-Types

Across their distribution, steelhead return to fresh water throughout the
year, with
seasonal peaks in migration activity. These seasonal peaks are used to name and
describe
various runs. In Alaska, the runs are called fall and spring; in British
Columbia, Washington,
Oregon, and California, the runs are usually called summer and winter. Large
rivers, such as
the Klamath and Rogue Rivers, may have adult steelhead migrating throughout the
year
(Shapovalov and Taft 1954, Rivers 1957, Barnhart 1986), with several vernacular
run names.
For example, what is now known as summer steelhead in the Rogue River was
historically
divided into spring and fall steelhead (Rivers 1963). Run-type designation for
steelhead in the
Klamath and Trinity Rivers continues to be perplexing, particularly with respect
to what is
historically called fall-run steelhead. Everest (1973) and Roelofs (1983)
contend that spring
and fall steelhead of the Rogue, Klamath, Mad, and Eel Rivers are in fact summer
steelhead
based on lack of segregation at spawning, and the observation that sport
fisheries for fall
steelhead are limited to rivers with summer steelhead. However, other biologists
classify fall
steelhead separately (e.g., Heubach 1992) or as winter steelhead. Roelofs (1983)
identified the
need for research to identify the relationship between fall-run and summer-run
steelhead of the
Klamath and Eel Rivers. In this document, spring- and fall-run steelhead of the
Klamath Basin
are considered summer steelhead.

Biologically, steelhead can be divided into two basic run-types, based on the
state of
sexual maturity at the time of river entry and duration of spawning migration
(Burgner et al.
1992). The stream-maturing type (fall-run in Alaska, summer-run elsewhere)
enters fresh
water in a sexually immature condition and requires several months in fresh water
to mature
and spawn. The ocean-maturing type (spring-run in Alaska, winter-run elsewhere)
enters
fresh water with well-developed gonads and spawns shortly thereafter. This
document uses the
terms summer-run or summer steelhead to refer to the stream-maturing type and
winter-run or
winter steelhead to refer to the ocean-maturing type.

In the Pacific Northwest, steelhead that enter fresh water between May and
October are
considered summer-run, and steelhead that enter fresh water between November and
April are
considered winter-run. Variations in migration timing exist between populations.
Some river
basins have both summer and winter steelhead, while others have only one
run-type.

Distribution of coastal steelhead run-types--It is difficult to
accurately describe the
historical distribution of coastal steelhead run-types due to the muddled history
of O. mykiss
taxonomy and local vernacular terms for steelhead of various run-times. Current
distribution
of coastal steelhead run-types is described in varying detail by several authors
(Roelofs 1983,
Barnhart 1986, Pauley et al. 1986, Burgner et al. 1992). Winter steelhead
utilize coastal
streams from Yakutat, Alaska to Malibu, California (Burgner et al. 1992). Summer
steelhead
are discontinuously distributed across the same range, presently extending as far
south as the
Middle Fork of the Eel River (Roelofs 1983). California Department of Fish and
Game
records indicate summer steelhead may have existed in the Sacramento Basin prior
to the
construction of several dams in the 1940s-1960s (McEwan and Jackson in prep.).
Table 3
shows the river basins in Washington, Oregon, and California that support natural
runs of
coastal summer steelhead alone and co-ocurring coastal summer and winter
steelhead.

Temporal and spatial separation of spawning--Although time of stream
entry is
generally well documented for summer and winter steelhead, there is relatively
little
information on time and location of spawning. Both summer and winter steelhead
spawn in
the winter to early spring. Difficult field conditions at that time of year and
the remoteness of
spawning grounds contribute to the lack of specific information on steelhead
spawning
(USFWS 1956, Roelofs 1983).

In drainages with both summer and winter steelhead, there may or may not be
temporal
separation of spawning between the two run-types. Based on tagging upstream
migrating
steelhead and surveying spawning areas, Everest (1973) described spawning for
Rogue River
summer steelhead as December-March and for winter steelhead as March-June; thus,
there is
some overlap. However, Everest stated that peak spawning activity for the
run-types was separated by about 60 days. Neave (1949) stated that the two
run-types of
steelhead in the Cowichan River, Vancouver Island, British Columbia, spawn in
January-March and April-May, respectively; this indicates temporal segregation of
these
spawning populations.

bClassification of Klickitat River steelhead as coastal or inland has
not been fully resolved.

Everest (1973) found that in the Rogue River Basin, winter steelhead
spawned in larger
streams than summer steelhead. Withler (1966) and Smith (1969) described
waterfalls on the
Coquihalla and San Juan Rivers in British Columbia that are barriers to winter
steelhead but
not summer steelhead. Burgner et al. (1992) reported that while marine
distribution of
summer and winter steelhead overlaps, they do exhibit some run-type specific
differences.
These differences probably reflect the difference in time of freshwater entry for
the two
run-types (Burgner et al. 1992); however, it is also possible that these are
differences between
coastal steelhead, which are primarily winter-run, and inland steelhead of the
Columbia Basin,
which are almost entirely summer-run.

Phenotypic characteristics--Smith (1969) conducted meristic counts
of vertebrae, gill
rakers, and lateral-line scales on summer and winter steelhead from eight coastal
streams in
British Columbia and Washington. Smith found no significant difference in these
features
between populations of the same run-type. When the data for populations of the
same run-type
were pooled, significant differences between run-types for all features except
lateral-line scale
count were found. Smith (1960, 1969) also artificially spawned wild summer and
winter
steelhead collected from the Capilano River, British Columbia to compare meristic
and
morphometric characteristics among and between their progeny; "crosses were not
made
between summer and winter fish" (Smith 1969, p. 23 and 24). Smith found that
some
meristic and morphometric characteristics, such as number of parr marks and
relative quantity
of visceral fat, were different between juveniles of the two run-types. Smith
stated that no
intergrades were found between the run-types for fat storage in yearling fish,
gonad
development in salt water, and quantity of fat relative to gonad development at
stream entry.
However, some characteristics were either not significantly different between
run-types or
were ambiguous. Smith concluded that the results of this study suggest recent
reproductive
isolation between summer and winter steelhead in the Capilano River.

Summer steelhead undergo morphological changes during their extended
spawning
migrations, developing red coloration on their opercula and lateral line similar
to those found
in rainbow trout; males also develop a kype (Snyder 1940; Smith 1960, 1969).
Smith (1969)
suggested that among sympatric populations of spawning summer and winter
steelhead, these
morphological characteristics may provide visual cues to prevent interbreeding
between the
run-types. Upon examination, Smith (1960) found that spawning summer steelhead
in the
Capilano River had flattened and bifurcated gill rakers. Capilano River winter
steelhead
demonstrated little development of rainbow coloration and lacked the flattened
and bifurcated
appearance of the gill rakers observed in summer steelead (Smith 1960).

Heritability of run-timing--Smith (1960) found that artificially
spawned and reared
offspring of wild summer and winter steelhead from the same river basin
maintained the
run-timing characteristics of their parents.

Genetic information on run-timing--Differentiation based on timing
of upstream
migration in steelhead has also been investigated by genetic methods. Allendorf
(1975) and
Utter and Allendorf (1977) found that summer and winter steelhead of a particular
coastal
stream tended to resemble one another genetically more than they resembled
populations of
adjacent drainages with similar run-timing. Later allozyme studies have
supported these
conclusions in a variety of geographical areas (Chilcote et al. 1980, Schreck et
al. 1986,
Reisenbichler and Phelps 1989), including the Rogue River (Reisenbichler et al.
1992).
However, in each of these more recent studies, the summer-run stocks have had
some hatchery
introgression and therefore may not represent the indigenous population.
Furthermore, in at
least some cases, interpretation of the results may be complicated by
difficulties in determining
run-timing of the sampled fish.

Thorgaard (1983) analyzed chromosomal variability in winter-run and
summer-run
steelhead from two rivers that had little history of hatchery introductions: the
Quinault River
in Washington and the Rogue River in Oregon. Chromosome number differed between
the
two river systems but was similar in summer and winter steelhead within each
river system.

Run-timing of Illinois River steelhead--The Illinois River is
generally considered to
have only winter steelhead (Jennings -
footnote 4). Historically, there may have been a weak run of
summer steelhead in the Illinois River (Rivers 1957). Recent Forest Service
records describe
the occurrence of one apparent summer steelhead in the Illinois Basin in 1990
(USFS 1992,
Busby et al. 1993). Whether the Illinois River at one time had its own run of
summer
steelhead, or whether summer steelhead observed in the river are actually
migrants from the
Rogue River, is not certain. Everest (1973) stated that prior to the
construction of the
flow-regulating Lost Creek Dam, summer steelhead from the Rogue River sought
thermal
refuge in the lower Illinois River; Everest (footnote 5) believes these may have been
the summer steelhead
that Rivers (1957) described in the Illinois River.

Age Structure

Steelhead exhibit a diverse array of life-history patterns with
variations in smolt age,
saltwater residence, and spawning activity. As a case in point, Oregon
Department of Fish
and Wildlife (ODFW) has identified 15 life-history patterns among wild summer
steelhead in
the Rogue River (ODFW 1994). The different life-history patterns are found at
different
frequencies among steelhead populations. The most common pattern for wild
coastal steelhead
south of Alaska is to smolt after 2 years in fresh water, then return to spawn
after 2 years in
salt water (Table 4 and 5), whereas
steelhead reared in hatcheries usually smolt at 1 year
(Chapman 1958, Lindsay et al. 1991). In Alaska, wild steelhead usually smolt at
3 years
(Sanders 1985). There may be a latitudinal cline to these life-history patterns
(Withler 1966),
with increases in age at smolting and spawning at higher latitudes (Table 4 and 5). Titus et
al. (in press) found no statistical evidence for a latitudinal cline in steelhead
smolt age from
California to British Columbia; however, they did find that saltwater age at
spawning (and
mean adult length) did increase with increasing latitude.

aO = Ocean maturing; S = Stream maturing (see Glossary, Appendix A).
bThese data are from adult fish collected in the lower Rogue River and
therefore may include
steelhead from the
Illinois and Applegate Rivers.

Steelhead may survive spawning, return to the ocean, and spawn again in
subsequent
years. Up to five spawning migrations have been recorded for individual
steelhead (Bali 1959,
Lindsay et al. 1991); however, more than two is unusual. Columbia River
steelhead are
essentially semelparous (Long and Griffin 1937, ODFW 1986), typically completing
only one
spawning migration. Repeat spawners are predominately female due to higher
post-spawningmortality among males (Shapovalov and Taft 1954, Maher and Larkin
1955, Chapman 1958,
Withler 1966, ODFW 1986, Burgner et al. 1992). Incidence of repeat spawning
tends to
decrease from south to north (Withler 1966), with much variation among
populations
(Table 6).

Half-Pounders

Steelhead with the life-history pattern called "half-pounder" (Snyder
1925) are
steelhead that return from their first ocean season to fresh water from July
through September,
after only 2 to 4 months of saltwater residence. They generally overwinter in
fresh water
before outmigrating again in the spring. There is some variability in criteria
for defining
half-pounders. Kesner and Barnhart (1972) described Klamath River half-pounders
as being
250-349 mm. Everest (1973) used 406 mm as the upper limit of half-pounder body
length on
the Rogue River.

The half-pounder migration has been termed a "false spawning run"
because few
half-pounders are believed to be sexually mature. However, Everest (1973) found
some
spawning activity by male half-pounders that were 355-406 mm in length.

Half-pounders are reported in the scientific literature from the
Rogue, Klamath, Mad,
and Eel River drainages of southern Oregon and northern California (Snyder 1925,
Kesner and
Barnhart 1972, Everest 1973, Barnhart 1986). Anecdotal accounts suggest that the
half-pounder life history may also occur outside of these basins. However, the
lack of either a
half-pounder fishery outside the Rogue, Klamath, Mad, and Eel Rivers or
scientific
documentation suggests that if it occurs in other locations, the half-pounder
strategy is less
successful than in the basins named above and occurs at a much lower frequency.

Half-pounders can migrate significant distances; for example,
half-pounders of Klamath
River origin have been found in the Rogue River (Everest 1973). It is apparently
common for
steelhead to make their half-pounder run into a nonnatal stream and then return
to their natal
stream to spawn as mature adults (Everest 1973, Satterthwaite 1988). A popular
sport fishery
has developed around the half-pounder runs in the Klamath and Rogue Rivers.

Half-pounders are generally associated with summer-run steelhead
populations.
However, this trait has also been identified in winter-run steelhead, albeit at a
lower
frequency. For example, Hopelain (1987) found a half-pounder frequency of 23.2%
among
lower Klamath River winter-run steelhead, as compared to a mean frequency of
95.2% among
fall-run (summer) steelhead from six Klamath River tributaries. Scale analysis
of Rogue River
winter steelhead initially collected for Cole Rivers Hatchery broodstock
indicated a half-
pounder frequency of approximately 30% (Evenson - footnote 6).

Presumably, the half-pounder life history occurs either to avoid a
deleterious condition
in the ocean or to exploit a beneficial condition inland. However, since
half-pounders were
first described in the literature (Snyder 1925), little additional information
has been published,
and no convincing theories to explain half-pounders have been advanced. It is
not known to
what degree this trait is due to genetic as opposed to environmental factors. In
initiating the
winter-run steelhead broodstock at Cole Rivers Hatchery (on the Rogue River),
scale patterns
were used to select fish that lacked the half-pounder life history (Evenson
footnote 6).
Recently, however, there is evidence of half-pounders among winter-run steelhead
returning to
the hatchery. Cramer et al. (1985, p. 112) stated that the "occurrence of the
half-pounder life
history has increased among winter steelhead released from Cole Rivers Hatchery
since the
time that growth rates of parr in the hatchery have been accelerated in order to
produce age 1
smolts." These findings suggest that the incidence of the half-pounder life
history can be
influenced by environmental conditions.

Illinois River steelhead scale data from ODFW (1992b) indicate that of
163 steelhead
angled between January 1982 and February 1990, 158 were mature adults and 5 (3%)
were
half-pounders. It is possible that the few half-pounders had roamed from their
natal stream
and were not of Illinois River origin. The ODFW data do not indicate whether any
of the
mature adults had scale patterns indicative of previous half-pounder runs.
Anglers have
reported to NMFS that half-pounders are indeed present, and caught, in the
Illinois River
(Beyerlin 1992, Leseman 1993).

Although half-pounders occur at a much lower frequency among Illinois
River
steelhead than Rogue River steelhead, the Illinois River is not unique among
coastal steelhead
streams in not having half-pounders. In fact, most steelhead populations
coastwide do not
have this life-history trait. We were unable to determine whether other river
basins besides the
Rogue River that have half-pounders (i.e., the Klamath, Mad, and Eel Rivers) have
tributaries,
like the Illinois River, in which the trait is rare or absent.

Oceanic Migration Patterns

Anadromous salmonids are known to demonstrate stock-specific
differences in oceanic
migrations. Examples of this are seen in data from coded-wire-tag recoveries of
hatchery
reared salmon (Table 7). Chinook (O. tshawytscha)
and coho (O. kisutch) salmon released
from ODFW hatcheries north of the Rogue River are recovered in the ocean off
Alaska,
British Columbia, and Washington at greater frequencies than are salmon from the
Rogue and Chetco Rivers. Conversely, southern Oregon stocks of salmon are
recovered in the ocean
fishery off California at greater frequencies than are the northern stocks.
Nicholas and Hankin
(1988) found that chinook salmon from Oregon rivers south of Cape Blanco (e.g.,
the Rogue
and Chetco Rivers) generally rear in the ocean off southern Oregon and northern
California,
while chinook salmon from Elk River and basins to the north generally rear in the
ocean as far
north as Alaska; these stocks are termed "south-migrating" and "north-migrating,"
respectively. An anomaly in this pattern is spring-run chinook salmon from the
Umpqua
River; Nicholas and Hankin refer to this as a "north-and-south-migrating" stock
because they
rear in the ocean from northern California to Alaska (Table 8).

*Difference between total recoveries for a given stock and 1.0 is the proportion
recovered in
freshwater sport and
gill-net fisheries, which ranged between 0.0 and 0.05.

Steelhead--There are several published reports on the
distribution and abundance of
steelhead during their saltwater phase (e.g., Sutherland 1973, Hartt and Dell
1986, Light et al.
1989, Pearcy et al. 1990). One might conclude that a great deal is known of the
ocean
ecology of steelhead. However, the appearance is deceptive because many of these
reports
utilize the same data set, that of the International North Pacific Fisheries
Commission. These
data are concentrated north of latitude 42°N and are collected primarily
between April and
October each year. Conclusions on the movements of steelhead are commonly drawn
from
very small sample sizes; for example, Pearcy and Masuda (1982) reported steelhead
migration
behavior based on 13 fish collected over 2 years. With these caveats, the
published
assumptions concerning steelhead behavior in the ocean are given below.

Several authors have concluded that juvenile steelhead move directly
offshore after
ocean entry (e.g., Pearcy and Masuda 1982, Miller et al. 1983, Hartt and Dell
1986, Pearcy
et al. 1990). Steelhead have been collected at longitude 145°W during their
first summer in
salt water; in their second ocean summer, steelhead have been collected at
longitude 180° (Pearcy and Masuda 1982). Other species of salmonids,
notably chinook and coho salmon,
tend to remain along the coast during their ocean migrations (Pearcy 1992).

aRiver is located south of Cape Blanco, Oregon.
bProvisional classification based on geographic location, limited
data, or both (Nicholas and
Hankin 1988).

Pearcy et al. (1990) observed that steelhead originating south of Cape
Blanco are rarely
recovered north of Cape Blanco in high seas and nearshore collections. Pearcy
(1992) stated
that southern stocks of coho salmon and steelhead "may not be highly migratory
and may feed
in the strong upwelling areas off northern California and southern Oregon rather
than migrate
long distances into productive subarctic waters" (p. 13).

Everest (1973) found evidence of summer steelhead straying between the
Rogue and
Klamath River Basins. Based on recapture data from summer steelhead tagged in
the Rogue
River, Everest (1973, p. 32) reported that "the primary offshore rearing areas of
Rogue
summer steelhead lie to the south, off the northern California coast. The area
could be shared
coincidentally with Klamath River stocks, which could explain the exchange of
fish between
the two river systems."

Summary of ocean information--Steelhead (also, coho and chinook
salmon) from
rivers south of Cape Blanco, Oregon, generally exhibit different ocean migration
patterns than
their conspecifics from rivers north of that geographic feature. Whereas the
northern
populations migrate north (e.g., to the Gulf of Alaska), populations south of
Cape Blanco
generally do not. One factor in this pattern may be the strong summer upwelling
in the ocean
south of Cape Blanco which provides highly productive ocean waters.

Straying

Based on tag returns, Everest (1973) found evidence of straying by
summer steelhead
between the Rogue and Klamath River Basins. Some of this straying was by
half-pounders,
but adults also strayed. According to Everest (1973, p. 31), "[s]trong physical
and behavioral
similarities exist between summer steelhead populations in the two systems and
strays from the
Rogue probably reproduce successfully with Klamath stocks."